Device for positioning a person&#39;s head in a coordinate system

ABSTRACT

In rhinostereometry, which is an optical method for measuring the congestion of the nasal mucosa, it has to be possible to repeatedly and with high accuracy fix the test subject&#39;s head in the same position in a coordinate system. This can be achieved by means of a fixing device comprising a plurality of pressure transducers (6-10) which are brought into contact with the test subject&#39;s head in such a manner that the head exerts at least a predetermined minimum pressure on all the transducers. Because the fixing device includes means for recording the positions of the pressure transducers in the coordinate system, the test subject&#39;s head can be repeatedly fixed in the same position.

This invention relates to a device for fixing a person's head in acoordinate system.

Rhinostereometry is an optical method used for measuring the congestionof the nasal mucosa. The head of the person to be subjected to suchmeasuring is fixed in a coordinate system. The positions in thecoordinate system of a number of points on the nasal mucosa aredetermined by means of a surgical microscope which is placed on amicrometer table and is movable in all three dimensions.

In order for rhinostereometry to repeatedly yield comparable results,the head of the person subjected to such measuring has to be fixed inthe same position on different occasions. Accurate fixation is of theutmost importance, since a point on the nasal mucosa moves about 4 mm atthe most when the mucosa changes from a state of minimum congestion toone of maximum congestion.

The object of the invention is to provide a device enabling repeated andhighly accurate fixation of a person's head in a coordinate system.

This object is achieved by a device having the distinctive featuresrecited in appended claim 1. With the inventive device, a person's headcan be fixed time after time in the same position in the coordinatesystem by setting the pressure transducers in previously recordedpositions in the coordinate system and ensuring that each transducer isacted on by a predetermined pressure from the person's head.

Fixation is facilitated and can be done more quickly if the pressuretransducers are disposed on a common support means which is movablyarranged on a frame and thus can be used for roughly positioning thepressure transducers.

Preferably, the support means has the shape of a spectacle frame, twopressure transducers being arranged as pad bridges. In fixation, the padbridges of the support means are moved downwards over the nasal bone aswhen glasses are put on.

Preferably, the remaining pressure transducers on the support means areso arranged as to be contacted with the forehead as well as the headclose to the eyes during fixation. This arrangement of the pressuretransducers is advantageous, in that the skull is here close beneath theskin, enabling more accurate fixation.

An embodiment of the invention will now be described in detail withreference to the accompanying drawing, in which

FIG. 1 schematically illustrates an embodiment of a fixing deviceaccording to the invention; and

FIG. 2 is an example of a pressure transducer to be used in theinventive device.

Thus, FIG. 1 shows an inventive fixing device comprising a verticallyadjustable table 1, on which are mounted a vertically adjustable chinrest 2 and a fixed frame 3. Two limbs 4, on which a spectacle frame 5 ismovably mounted, are fixedly arranged on the frame 3. The spectacleframe 5 can be fixed in different positions on the limbs 4, and itsposition thereon can be recorded by means provided therefor (not shown).Five pressure transducers 6-10 are mounted on the spectacle frame, butare merely schematically illustrated in the drawing in the form of"buttons". Two pressure transducers 6, 7 form pad bridges for thespectacle frame and are adapted to be contacted with the test subject'sface at the nasal bone in the same manner as the pad bridges of ordinaryglasses. A pressure transducer 8 is provided at the upper edge of thespectacle frame 5 so as to come into contact with the test subject'sforehead when the pressure transducers 6, 7 in the form of pad bridgescontact the nasal bone. The other two pressure transducers 9, 10 areprovided at the side edges of the spectacle frame 5 and are adapted tocome into contact with the test subject's face close to the eyes wherethe skull is just beneath the skin. For instance, the pressuretransducers may have a surface of engagement with the face of about 3mm². Naturally, the number of pressure transducers and their positionsmay vary.

FIG. 2 shows by way of example the design of a pressure transducer thatmay be used in the device of FIG. 1. The pressure transducer has a fixedholder 20, and a pressure-sensing unit 21 slidably mounted therein. Thepressure-sensing unit 21 has a pressure-sensitive end portion 22 adaptedto be contacted with the test subject's face. The pressure exerted bythe face on the pressure-sensitive end portion 22 is recorded by meansprovided therefor (not shown), which emit a signal, e.g. turn on alight-emitting diode 23, when a given minimum pressure has beenattained. A locking means 24 is adapted, in a first position, to fix thepressure-sensing unit 21 and, in a second position, to allowdisplacement of the pressure-sensing unit 21 in the holder 20. Theposition of the pressure-sensing unit 21 in the holder can be read on ascale 25 which is provided on the holder 20.

Naturally, the pressure transducers can be designed in many differentways. The main thing is that the positions of the pressure transducersin the coordinate system can be recorded and a signal be obtained whenthe test subject's head exerts at least a predetermined minimum pressureon the transducers. Advantageously, the pressure transducers areconnected to a means that indicates when at least the predeterminedminimum pressure is exerted on all the pressure transducers.

When a test subject is to undergo rhinostereometry for the first time,he puts the chin against the chin rest 2, and the spectacle frame 5 ismoved downwards so as to apply the pressure transducers 6, 7 against thenasal bone with at least a predetermined minimum pressure. Then, theother pressure transducers 8-10 are so set that the minimum pressure isattained. The position of the spectacle frame 5 on the limbs 4 isrecorded, as are the positions of the pressure transducers 6-10.

When the test subject is again to undergo rhinostereometry andcomparable results are to be obtained, the spectacle frame 5 is placedon the limbs 4 in the position previously recorded. Also the pressuretransducers 6-10 are arranged in the positions previously recorded.Thereafter, the test subject puts his face against the spectacle frame,so that all the pressure transducers indicate that the minimum pressurehas been attained, the test subject's face being now fixed in the sameposition in the coordinate system as in the first measurement, enablingcomparable results to be obtained.

I claim:
 1. A device for fixing a person's head in a coordinate system,comprising:a plurality of pressure transducers, the pressure transducersbeing movable in the coordinate system and being adapted to be contactedwith the person's head when fixing the person's head in the coordinatesystem; means, associated with each of the pressure transducers, fordetecting when the transducers are acted on by at least onepredetermined pressure from the person's head; support means on whichthe plurality of pressure transducers is fixed; a frame fixedly arrangedin the coordinate system, the support means being movably mounted on theframe; and means for recording positions of the pressure transducers inthe coordinate system, wherein the support means has the shape of aspectacle frame having two eye holes and two pressure transducers, thetwo pressure transducers being arranged as pad bridges to be contactedwith a nasal bone of the person's head by moving the nasal bone of theperson's head into contact with the two pressure transducers.
 2. Adevice as set forth in claim 1, at least one of the pressure transducersis so positioned on the support means as to be contacted with a foreheadof the person's head during fixation of the person's head in thecoordinate system, and at least two of the pressure transducers are sopositioned on the support means as to be contacted with regions of theperson's head close to the eyes.
 3. A device as set forth in claim 1,wherein the detecting means associated with the pressure transducers areconnected to an indicator means for indicating when all the transducersare acted on by at least the predetermined pressure.
 4. A device as setforth in claim 2, wherein the detecting means associated with thepressure transducers are connected to an indicator means for indicatingwhen all the transducers are acted on by at least the predeterminedpressure.